Synergistic antibacterial effect of ethanolic extract of Carica papaya and Psidium guajava leave extract on Salmonella typhi, Escherichia coli and Klebsiella pneumoniae

This study assessed the synergistic antibacterial effect of ethanol extract of Carica papaya and Psidium guajava on Salmonella typhi, Escherichia coli and Klebsiella pneumoniae using agar well diffusion method and microdilution with Microtitre plates. Qualitative phytochemical analysis of the extract reveals the presence of alkaloids, saponins, glycosides, steroids, soluble carbohydrates and phenols. Five (5) grams of the freeze-dried extract was dissolved in 10ml of 10% Dimethyl Sulphoxide (DMSO) and used for sensitivity against selected standard isolates. Upon sensitivity testing, this study observes a significant inhibition zone diameter at the highest concentration of the extract (500 mg/ml) against Klebsiella pneumoniae with an inhibition zone diameter of 31.0mm relative to the inhibition zone diameters of Escherichia coli and Salmonella typhi with (19.5 mm) and (20.5 mm) respectively. The inhibition zone diameters of the positive control (ciprofloxacin solution) at 500 mg/mL for Klebsiella pneumoniae, Escherichia coli and Salmonella typhi was 36.0 mm, 37.5 mm and 34.5 mm respectively. Escherichia coli has minimal inhibitory concentration (MIC) of 0.977 mg/ml while Klebsiella pneumoniae and Salmonella typhi have their minimal inhibitory concentration (MIC) at 31.25 mg/ml and 62.5 mg/ml respectively.